1. Field of the Invention
This invention relates to certain tertiary aromatic amines which are unique in their application as accelerators for the peroxide catalyzed polymerization of acrylic resins. The tertiary aromatic amine accelerators of the present invention are derived either from aminoglutethimide or from para-aminophenylacetic acid. The polymerized acrylic resin compositions are particularly useful in dentistry as improved restorative materials, with or without the addition of reinforcing fillers, and in medicine as orthopedic bone cements.
2. Background of the Invention
Aminoglutethimide, the basic compound from which one class of the amines of the present invention are derived, is known in the literature as an anticonvulsant and potent inhibitor of steriod biosynthesis, rather than as an accelerator for peroxide catalyzed acrylic resin polymerization. Hanson, Ballonoff & Northcutt, 230 J. Am. Med. Assn. 963 (1974); The Merck Index 56 (8th ed. Stecher 1968); U.S. Pat. No. 2,848,455. With respect to the second class of tertiary aromatic amines employed in the present invention, the lower molecular weight homologues of the amines derived from para-aminophenylacetic acid are recognized in the literature as having limited usefulness as chemical intermediates and anti-inflammatory agents, rather than as polymerization accelerators. Everett, Roberts & Ross, J. Chem. Soc. 2386 (1953); Tadros, Sakla & Awad, 315 J. Prakt. Chem. 1002 (1973); Tuzun, 13 Commun. Fac. Sci., Univ. Ankra, Ser. B. Chim. 41 (1966); Wall, Abernathy, Carroll & Taylor, 12 J. Med. Chem. 810 (1969); U.S. Pat. Nos. 3,789,123 & 3,657,230; German Pat. Nos. 1,913,742 & 2,223,855.
The use of other selected amines, especially simple amines, in conjunction with peroxides to bring about polymerization of acrylic resins has been known since 1940 or earlier. See German Pat. No. 760,351 to E. Schnebel. Certain acrylic resin/peroxide/aromatic amine poymerization systems have been employed in the past in the dental and medical arts. See for example, Guide to Dental Materials and Devices 113 (7th ed. 1974-75); Guide to Dental Materials and Devices 112 (6th ed. 1972-73); Lal & Green, 17 J. Polym. Sci. 403 (1955); F. Peyton & R. Craig, Restorative Dental Materials 441 (4th ed. 1971); R. Phillips, Skinner's Science of Dental Materials 193-94, 219-20 (7th ed. 1973); U.S. Pat. No. 2,558,139. A peroxide-free system is shown in U.S. Pat. No. 3,541,068. Tertiary amines with an aniline skeleton and higher molecular weight nitrogen substituents are suggested for use in dental materials in U.S. Pat. No. 3,740,850, Bowen & Argentar, 50 J. Dent. Ref. 923 (1971), and Bowen & Argentar, 51 J. Dent. Ref. 473 (1972). The use of tertiary amines as accelerators in conjunction with ethylenically unsaturated monomers and catalysts in other technological areas, such as in the areas of ink vehicles, wax compositions, metal adhesives, coatings and anaerobic sealants are shown in U.S. Pat. Nos. 3,966,573; 3,790,541; 3,629,220; 3,634,379; 3,594,354 and 3,682,875. See also Mleziva, 15 Chem. Prum. 80 (1965); Mleziva, 1 Plast. Hmoty. Kauc. 225 (1964); U.S. Pat. Nos. 3,631,009; 3,525,725.
However, as has been documented in the literature, the aromatic amines previously used for acceleration of the peroxide catalyzed polymerization of acrylic resins have been characterized by a number of major disadvantages with respect to their use especially in dental materials. Some fail to cause rapid hardening at room temperature, a necessary property for a resin composition which is to be employed in medical or dental work. A number result in composites with poor resistance to mechanical wear, which is a serious drawback in a dental material which will be subjected to the pressures of chewing and grinding.
In general, the amines used previously have tended to introduce undesirable coloration into the dental material upon initiation of polymerization. See Bowen & Argentar, 51 J. Dent. Res. 473 (1972); Bowen & Argentar, 50 J. Dent. Res. 923 (1971); Bowen & Argentar, 75 J. Amer. Dent. Assn. 918 (1967); Brauer, Davenport & Hansen, 34 Mod. Plast. 153 (1956). Prior art accelerators have also exhibited lack of color stability upon exposure of the specimen containing the compound to either visible or near-visible ultraviolet light (such as sunlight) over a period of time. Such exposure would occur as a matter of course for resin compositions employed as dental materials. Since the cosmetic appearance of restorative dental work (e.g., crowns) is very important to the patient, these difficulties are of considerable concern in the field of dentistry.
Furthermore, it is suspected that, because of their toxicity, aromatic amines are involved in eliciting an unfavorable dental pulp response to the final polymerized resin composition. See Bowen & Argentar, 51 J. Dent. Res. 473 (1972); U.S. Pat. No. 3,740,850. The toxicity of the amines to surrounding tissues would also be an important consideration in choice of orthopedic bone cements.